20.3.2.a. Water Balance Method

Try these first

1. 1.

   What does P represent in the Water Balance Method?

   Hint

   Think of the water that falls from the sky.

2. 2.

   In the formula ET = P - R - D - ΔS, what does ΔS stand for?

   Hint

   Consider how much water is retained in the soil after a rain.

3. 3.

   What does R stand for in the Water Balance equation?

   • Runoff
   • Residuals
   • Rainfall

   Hint

   Think about what happens to water that doesn’t stay in the soil.

4. 4.

   The Water Balance Method helps estimate how much water is available for evapotranspiration. True or False?

   Hint

   Consider the purpose of the method.

5. 5.

   Given a hypothetical basin receives 500 mm of precipitation, has 150 mm runoff and experiences a decrease in soil water storage of 100 mm, calculate the ET using the Water Balance Method.

   Hint

   Watch out for the negative sign indicating an increase in soil water storage.

6. 6.

   Discuss how climate change might affect parameters in the Water Balance Method in your local region and predict possible impacts on agriculture.

   Hint

   Consider how each element of the water cycle is intertwined.